1. Field of the Invention
The present invention relates to a shape memory alloy actuator system which includes a shape memory alloy actuator.
2. Description of the Related Art
A shape memory alloy undergoes a phase transition (phase change) due to a change in a temperature, and has a change of shape. An actuator in which, the shape change of the shape memory alloy is used is superior in characteristics such as a small size and a light weight. For instance, an actuator described in Japanese Patent Application Laid-open Publication No. Hei 7-274561 is available as a conventional example of an actuator in which a shape memory alloy is used. In the actuator described in Japanese Patent Application Laid-open Publication No. Hei 7-274561, the shape is changed by adjusting a heating and a cooling of the shape memory alloy by adjusting a supply of an electric power to the shape memory alloy. Moreover, the shape change of the shape memory alloy is controlled by controlling a feedback by using a resistance value which changes with the shape change. In Japanese Patent Application Laid-open Publication No. Hei 7-274561, a technology in which the actuator functions as a sensor by carrying out a resistance feedback control has been disclosed.
However, in a shape memory alloy actuator, in a case of carrying out a control of a mobile object of the actuator by controlling an amount of electric power supplied to the shape memory alloy by the feedback control, a value of a feedback gain is strongly affected by a position controllability and a response speed of the mobile object which is coupled with the shape memory alloy. Furthermore, when a use environment of the actuator is changed, there is a possibility that the optimum feedback gain changes according to use due to a change in an external temperature around the actuator and a wearing out of constituent members. Therefore, for carrying out a stable control every time, it is desirable to carry out the control by the optimum feedback gain according to the use. However, the actuator described in Japanese Patent Application Laid-open Publication No. Hei 7-274561 is not capable of coping with this point.